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Naming Binary and Ionic Inorganic Compounds

1. When writing formulas for binary compounds, elements are arranged in order, except for H, O, and F. The accepted order by groups and these elements is:

1A < 2A < 3A < 4A < 5A < H < 6A < 7A < O < F

2 Determine whether the compounds is ionic or molecular:

(a) Binary compounds of two , two metalloids, or a metalloid and a are usually molecular.

(b) Binary compounds of a and a nonmetal are usually ionic.

(c) A compound that contains a polyatomic cation or anion and any kind of counter (monatomic or polyatomic anion or cation) is ionic.

(d) Molecular compounds are named from their molecular formulas; ionic compounds are named from their empirical formulas.

3. For molecular compounds, name the first element followed by the stem of the second element plus "ide". Use Greek prefixes to indicate numbers of each atom in the molecular formula. (If there is only one of the first element, "mono" is not used.) Examples:

NO2 dioxide ("mono" not needed) N2O4 dinitrogen tetroxide ("a" of "tetra" usually dropped) SCl4 tetrachloride H2S (di) ("di" not needed, since no other HS compound exists) H2O water (not systematically named) NH3 ammonia (not systematically named) CH4 methane (not systematically named)

4. For ionic compounds, name the first element followed by the stem of the second element plus "ide", but do not use Greek prefixes to indicate numbers of atoms (unless a Greek prefix is a part of a complex ion's name). If a cation might have one of two or more possible charges, the charge is indicated by using a Roman numeral (Stock system). Examples:

LiF lithium fluoride

BaBr2 bromide ("di" not used) NaCN sodium cyanide (must know CN– = cyanide) 2+ Hg2Cl2 (I) chloride (Hg2 = mercury(I) ion, a diatomic ion) NH4NO3 ammonium NH4NO2 ammonium nitrite FeCl2 (II) chloride (formerly, ferrous chloride) FeCl3 iron(III) chloride (formerly, ferric chloride)